Charging apparatus

ABSTRACT

A charging apparatus includes: a connecting unit; a charging unit; a temperature detecting unit; and an operation inhibiting unit. The connecting unit is electrically connected to a power supply portion installed inside a vehicle. The charging unit supplies at least a part of electric power supplied from the power supply portion via the connecting unit to a battery thereby to charge the battery. The operation inhibiting unit inhibits operation of a battery circuit provided in the battery when an ambient temperature detected by the temperature detecting unit has reached a preassigned designated temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation of application Ser. No. 12/385,053 filed Mar. 30,2009, which claims the benefit of Japanese Patent Application No,2008-098283 filed Apr. 4, 2008. The disclosure of the prior applicationsis hereby incorporated by reference herein in its entirety.

BACKGROUND

The present invention relates to a charging apparatus that charges abattery.

Some of conventional electric power tools, which include a detachablebattery, are adapted to be driven by electric power supplied from thebattery. In such an electric power tool, the battery is charged by acharging apparatus separately provided from the electric power tool.

One example of a charging apparatus is disclosed in Unexamined JapanesePatent Publication No. 06-153418. The charging apparatus detects atemperature of the charging apparatus and a temperature of the battery.When a predetermined time elapses in a state where an increase rate of adifference between the temperatures of the charging apparatus and thebattery has reached a predetermined value, the charging apparatusdetermines that the battery is fully charged and stops charging thebattery.

SUMMARY

Convenience of the above described electric power tool can be improvedif the charging apparatus of the above example is configured to be ableto receive electric power from a vehicle in order to charge the batteryof the electric power tool.

The temperature inside the vehicle (especially when the vehicle isclosed) can increase to extremely high temperature when the temperatureoutside the vehicle (external temperature) is high or when the vehicleis exposed to sunlight. If an electronic circuit (battery circuit)included in the battery is operated inside the vehicle under extremelyhigh temperature, trouble may possibly occur to the battery circuit.

The aforementioned charging apparatus operates the battery circuit untila predetermined time elapses in a state where an increase rate of adifference between the temperatures of the charging apparatus and thebattery has reached a predetermined value, even if the temperatureinside the vehicle is extremely high. Thus, trouble may occur to thebattery circuit when the charging apparatus is used in such anenvironment.

In one aspect of the present invention, it would be desirable that acharging apparatus that receives electric power from a vehicle to chargea battery suppresses causing trouble to a battery circuit by operatingthe battery circuit although an ambient temperature has reached apreassigned designated temperature.

A charging apparatus in a first aspect of the present invention includesa connecting unit, a charging unit, a temperature detecting unit, and anoperation inhibiting unit. The connecting unit is electrically connectedto a power supply portion installed inside a vehicle. The charging unitsupplies at least a part of electric power supplied from the powersupply portion via the connecting unit to a battery thereby to chargethe battery. The temperature detecting unit detects an ambienttemperature. The operation inhibiting unit inhibits operation of abattery circuit as an electronic circuit provided in the battery whenthe temperature detected by the temperature detecting unit has reached apreassigned designated temperature.

In the above described charging apparatus, if the ambient temperaturereaches the designated temperature, the operation of the battery circuitis inhibited. Thus, it is possible to suppress causing trouble to thebattery circuit by operating the battery circuit although the ambienttemperature has reached the designated temperature.

The ambient temperature may include temperatures of spaces outside andinside the charging apparatus. The designated temperature can be anytemperature. For example, if the designated temperature is a maximumtemperature which is allowable for the battery circuit to operate or atemperature lower than the maximum temperature, the operation of thebattery circuit at the maximum temperature can be inhibited.

The connecting unit may be connected to any power supply portioninstalled inside a vehicle. For example, the connecting unit may beconfigured to be electrically connected to a cigarette lighter socketprovided inside the vehicle in order to supply electric power to acigarette lighter for lighting a cigarette.

If the connecting unit is configured as such, the charging apparatus caneasily obtain electric power from the cigarette lighter socket normallyprovided inside the vehicle.

The operation inhibiting unit may inhibit the operation of the batterycircuit in any manner. For example, if the charging apparatus isprovided with a power supply unit that supplies electric power to thebattery circuit, the operation inhibiting unit may inhibit the operationof the battery circuit by interrupting power supply from the powersupply unit to the battery circuit.

In this case, the operation of the battery circuit can be reliablyinhibited by interrupting power supply to the battery circuit.

The battery may be provided with at least one power supply terminal forelectrically connecting the battery to the power supply unit andsupplying electric power supplied from the power supply unit to thebattery circuit. In this case, the operation inhibiting unit may inhibitthe operation of the battery circuit by interrupting electricalconnection between the power supply unit and the at least one powersupply terminal.

The charging apparatus may include an electric signal communicating unitthat communicates electric signals with the battery circuit, and thebattery may be provided with at least one connecting terminal forelectrically connecting the electric signal communicating unit and thebattery circuit. In this case, it is preferable that the operationinhibiting unit sets a potential of the at least one connecting terminalto a protective potential by which the battery circuit can beelectrically protected, when inhibiting the operation of the batterycircuit.

In the operation inhibiting unit configured as above, even when avoltage generated by any cause is applied to the at least one connectingterminal in a state where the battery circuit is not operated, it ispossible to suppress causing trouble to the battery circuit by theapplied voltage.

In this case, it is preferable that the operation inhibiting unitincludes an inhibition signal outputting unit, an interrupting unit, anda protective potential setting unit.

In the operation inhibiting unit configured as such, the inhibitionsignal outputting unit outputs an inhibition signal that inhibits theoperation of the battery circuit when inhibiting the operation of thebattery circuit. When the inhibition signal is outputted from theinhibition signal outputting unit, the interrupting unit interruptselectrical connection between the power supply unit and the at least onepower supply terminal. When the electrical connection between the powersupply unit and the at least one power supply terminal is interrupted bythe interrupting unit, the protective potential setting unit sets apotential of the at least one connecting terminal to a protectivepotential.

In this case, power supply to the battery circuit can be interrupted andthe potential of the at least one connecting terminal can be set to theprotective potential, in synchronization with the output of theinhibition signal. In other words, as compared to the case in which theinterruption of power supply to the battery circuit is not synchronizedwith the setting of the potential of the at least one connectingterminal to the protective potential, the battery circuit can beefficiently protected.

The protective potential may be any potential as long as the batterycircuit can be electrically protected by the potential. For example, itis preferable that the protective potential is a reference potential ofthe battery circuit.

In this case, even if a voltage generated by any cause is applied to theat least one connecting terminal, a current generated by the voltagedoes not flow into the battery circuit. The battery circuit can bereliably protected.

The charging apparatus may be provided with a battery attaching portionthat detachably attaches the battery to the charging apparatus. Also,the battery can be used in any apparatus. For example, the battery maybe used in an electric power tool.

A recording medium in a second aspect of the present invention can beread by a computer which is provided in a charging apparatus including:a temperature detecting unit that detects an ambient temperature; and acharging unit that charges a battery, and stores a program that causesthe computer to execute a detection value obtaining step and anoperation determining step. Then the recording medium is read by thecomputer and this program is executed by the above described computer,the computer obtains a detection value of the ambient temperature fromthe temperature detecting unit in the detection value obtaining step,and determines whether or not the detection value obtained in thedetection value obtaining step has reached a preassigned designatedtemperature in the operation determination step. Then the detectionvalue has not reached the designated temperature, the computer permitsoperation of the battery circuit as an electronic circuit provided inthe battery, while, when the detection value has reached the designatedtemperature, the computer inhibits the operation of the battery circuit.

In other words, according to the recording medium that stores such aprogram, the computer can function as the operation inhibiting unit inthe charging apparatus of the first aspect of the present invention.

The computer may inhibit the operation of the battery circuit in anymanner in the aforementioned operation determination step. For example,the computer may inhibit the operation of the battery circuit byoutputting an inhibition signal which inhibits the operation of thebattery circuit.

The above described computer may be a known computer or a computersuitably configured for the charging apparatus of the first aspect ofthe present invention.

Also, the aforementioned recording medium may be of any type as long asthe recording medium is readable by a computer. Such recording mediumincludes, for example, any types of semiconductor elements (e.g., ROM,RAM, EEPROM, flash memory) that can store a program, a flexible disk(FD), an optical disk (MO), a DVD, a CD-ROM, a Blu-Ray disk, a HD-DVD, ahard disk, a USB memory, a memory card, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view showing a front side appearance of acharging apparatus according to the present invention;

FIG. 2 is a perspective view showing a back side appearance of thecharging apparatus;

FIG. 3 is a block diagram of a charging circuit provided in a main bodyof the charging apparatus;

FIG. 4 is a circuit diagram showing details of a temperature detectioncircuit and an operation control circuit included in the chargingcircuit;

FIG. 5 is a flowchart showing a flow of a battery circuit protectionprocess executed by a control unit included in the charging circuit;

FIG. 6 is an explanatory view simply illustrating operation of thecontrol unit and the operation control circuit when an ambienttemperature is lower than a designated temperature; and

FIG. 7 is an explanatory view simply illustrating the operation of thecontrol unit and the operation control circuit when the ambienttemperature has reached the designated temperature.

As shown in FIG. 1, a charging apparatus 1 of the present inventionincludes a cigarette lighter plug (hereinafter, simply referred to as aplug) 11, a power supply cord 12, and a main body 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The plug 11 is designed to be received by a cigarette lighter socket(hereinafter, simply referred to as a socket) 30 provided in a vehicle(see FIG. 3) in order to supply electric power to a not shown cigarettelighter for lighting a cigarette. The plug 11 is electrically connectedto the socket 30 when received by the socket 30.

The power supply cord 12 is electrically connected to the plug 11 at oneend and to the main body 13 at the other end. The power supply cord 12transmits electric power supplied from the socket 30 via the plug 11 tothe main body 13 when the plug 11 is electrically connected to thesocket 30. The socket 30 is electrically connected to a not shownbattery mounted on the vehicle. Electric power of the vehicle battery(for example, direct current (DC) 12V or 24V) is supplied via the socket30 to the plug 11.

The main body 13 includes an attachment portion 131 and a displayportion 132. The attachment portion 131 is configured such that abattery 40 (see FIG. 3) of an electric power tool can be attached to ordetached from the main body 13 in a sliding manner.

More particularly, as shown in FIG. 2, the attachment portion 131includes a protection cover 131A, a connector 131B, and a pair ofcharging terminals 131C and 131D.

The protection cover 131A is slidably provided with the attachmentportion 131 so as to cover the connector 131B and the charging terminals131C and 131D when the battery 40 is not attached to the attachmentportion 131, and to expose the connector 131B and the charging terminals131C and 131D to the battery 40 when the battery 40 is attached to theattachment portion 131.

The connector 131B includes: at least one output terminal (not shown)for supplying electric power to a battery circuit 42 (see FIG. 3) whichis an electronic circuit provided in the battery 40; a plurality ofinput terminals (not shown) for receiving signals from the batterycircuit 42; and a reference potential terminal for setting a referencepotential of the battery circuit 42.

The charging terminals 131C and 131D are electrically connected to acell 41 (see FIG. 3) provided in the battery 40 when the battery 40 isattached to the attachment portion 131 and supply electric power to thecell 41.

The display portion 132 includes three LEDs 132A, 132B and 132C whichdisplay a charged state and others of the battery 40 attached to themain body 13. In FIG. 2, depiction of the plug 11 is omitted.

Referring to FIG. 3, a charging circuit 20 provided in the main body 13includes a converter 21, a control IC 22, a temperature detectioncircuit 23, a control unit 24, and an operation control circuit 25.

The converter 21 is electrically connected to the plug 11 via the powersupply cord 12 at its input stage and to a cell 41 inside the battery 40attached to the main body 13 at its output stage. The converter 21 is aso-called DC-DC converter which converts a DC power supplied from thesocket 30 via the plug 11 into a DC power adapted to charge the cell 41of the battery 40. The battery 40 is charged by supplying the convertedDC power (charging current) to the cell 41.

The control IC 22 controls operation of the converter 21 (for example,ON/OFF and others of the charging current) based on a control signaloutputted from the control unit 24.

The temperature detection circuit 23 detects an ambient temperaturearound the temperature detection circuit 23, more particularly, aninternal temperature of the main body 13, thereby to output atemperature detection signal indicating the detected temperature to thecontrol unit 24.

The control unit 24 of the present embodiment is a known microcomputerincluding at least a CPU 241, a ROM 242, a RAM 243, an input/output(I/O) port 244 and an analog/digital (AID) converter 245. In the controlunit 24, the CPU 241 executes various processes according to variousprograms stored in the ROM 242 thereby to control respective portions ofthe charging circuit 20. In the control unit 24, analog signals inputtedto an input port of the I/O port 244 are converted to digital values bythe AID converter 245. The converted digital values are read by the CPU241.

The operation control circuit 25 controls operation of the batterycircuit 42 provided in the battery 40, based on a designated temperaturedetection signal outputted from the control unit 24. More particularly,the operation control circuit 25 turns ON/OFF power supply to thebattery circuit 42. The operation control circuit 25 also outputs analogsignals and digital signals outputted from the battery circuit 42 to thecontrol unit 24.

FIG. 4 shows details of the temperature detection circuit 23 and theoperation control circuit 25. As shown in FIG. 4, the temperaturedetection circuit 23 includes a thermistor TM1, resistors R10 and R11,and a capacitor C1.

The thermistor TM1 is a resistor which changes its resistance valuedepending on an ambient temperature around the thermistor TM1. Thethermistor TM1 of the present embodiment is a resistor which decreasesits resistance value as the ambient temperature around the thermistorTM1 is increased. The thermistor TM1 may be a resistor which increasesits resistance value as the ambient temperature around the thermistorTM1 is increased.

The thermistor TM1 is connected to a DC power source Vcc of the chargingcircuit 20 via the resistor R10 at one end, and to a GND line which isset to a reference potential (GND) of the charging circuit 20 at theother end. The DC power source Vcc of the present embodiment isconstituted by a DC-DC converter which converts a DC power supplied fromthe socket 30 via the plug 11 into a DC power suitable for the chargingcircuit 20.

The resistor R11 is connected to between the thermistor TM1 and theresistor R10 at one end, and to the I/O port 244 (more particularly, tothe input port) of the control unit 24 at the other end.

The capacitor C1 is connected to the other end of the resistor R11 atone end, and to the GND line at the other end. That is, the capacitor C1and the resistor R11 forms a low pass filter which removes electricalnoise having high frequency.

In the temperature detection circuit 23 configured as above, voltage ofthe DC power source Vcc is divided by the resistor R10 and thethermistor TM1. The divided voltage is outputted to the control unit 24as the aforementioned temperature detection signal in analog form. Inthe temperature detection circuit 23 of the present embodiment, thethermistor TM1 has the aforementioned characteristics. Thus, when theambient temperature around the temperature detection circuit 23 isincreased, the voltage of the temperature detection signal is decreased,while the ambient temperature around the temperature detection circuit23 is decreased, the voltage of the temperature detection signal isincreased.

The operation control circuit 25 includes switch circuits SW1 and SW2.

The switch circuit SW1 includes transistors Q1 and Q2 and resistors R1,R2, R12 and R13.

The transistor Q1 is a PNP bipolar transistor. The DC power source Vccis connected to an emitter of the transistor Q1. A power supply terminal43 provided in the battery 40 is connected to a collector of thetransistor Q1. The power supply terminal 43 is a terminal for supplyingDC power of the DC power source Vcc to the battery circuit 42. Theemitter of the transistor Q1 is connected to a base of the transistor Q1via the resistor R1.

The transistor Q2 is a NPN bipolar transistor. The GND line is connectedto an emitter of the transistor Q2. The base of the transistor Q1 isconnected to a collector of the transistor Q2 via the resistor R2. Theemitter of the transistor Q2 is connected to a base of the transistor Q2via the resistor R13. The I/O port 244 (more particularly, the outputport) of the control unit 24 is connected to the base of the transistorQ2 via the resistor R12. From the output port, the aforementioneddesignated temperature detection signal is outputted. The designatedtemperature detection signal of the present embodiment is a binaryvoltage signal by which a logic level of voltage is set to either “High”(for example, DC 5V) or “Low” (for example DC 0V).

In the switch circuit SW1 configured as above, when the logic level ofthe designated temperature detection signal is set to “High”, electriccurrent flows between the base and the emitter of the transistor Q2thereby to turn ON the transistor Q2. When the transistor Q2 is turnedON, electric current flows between the emitter and the base of thetransistor Q1 thereby to turn ON the transistor Q1. Thus, the DC powersource Vcc and the power supply terminal 43 are electrically connected.DC power of the DC power source Vcc is then supplied to the batterycircuit 42 via the power supply terminal 43.

On the other hand, when the logic level of the designated temperaturedetection signal is set to “Low”, electric current flowing between thebase and the emitter of the transistor Q2 is interrupted thereby to turnOFF the transistor Q2. When the transistor Q2 is turned OFF, electriccurrent flowing between the emitter and the base of the transistor Q1 isinterrupted thereby to turn OFF the transistor Q1. Thus, the DC powersource Vcc and the power supply terminal 43 are electricallydisconnected.

The switch circuit SW2 includes transistors Q3 and Q4 and resistors R3,R4, R5, R6, R7, R8, R9, R14, R15, R16 and R17.

The transistor Q3 is a NPN bipolar transistor. The GND line is connectedto an emitter of the transistor Q3. The DC power source Vcc is connectedto a collector of the transistor Q3 via the resistor R5.

The collector of the transistor Q1 is connected to a base of thetransistor Q3 via the resistor R14. The emitter of the transistor Q3 isconnected to the base of the transistor Q3 via the resistor R15.

The transistor Q4 is a NPN bipolar transistor. The GND line is connectedto an emitter of the transistor Q4. The DC power source Vcc is connectedto a collector of the transistor Q4 via the resistor R4.

The collector of the transistor Q3 is connected to a base of thetransistor Q4 via the resistor R16. The emitter of the transistor Q4 isconnected to the base of the transistor Q4 via the resistor R17.

The resistor R3 is connected to the 110 port 244 (more particularly, theinput port) of the control unit 24 at one end, and to the collector ofthe transistor Q4 and to an analog signal terminal 44 provided in thebattery 40 at the other end. The analog signal terminal 44 is a terminalfor outputting analog signals outputted from the battery circuit 42 tothe control unit 24.

The resistor R8 is connected to the I/O port 244 (more particularly, theinput port) of the control unit 24 at one end, and to a digital signalterminal 45 provided in the battery 40 at the other end. The digitalsignal terminal 45 is a terminal for outputting digital signalsoutputted from the battery circuit 42 to the control unit 24. Theresistor R8 is also connected to the collector of the transistor Q1 viathe resistor R6 at the one end.

The resistor R9 is connected to the 110 port 244 (more particularly, theinput port) of the control unit 24 at one end, and to another digitalsignal terminal 46 provided in the battery 40 at the other end. Thedigital signal terminal 46 is a terminal for outputting another digitalsignals outputted from the battery circuit 42 to the control unit 24.The resistor R9 is also connected to the collector of the transistor Q1via the resistor R7 at the one end.

In the switch circuit SW2 configured as above, when the transistor Q1 ofthe switch circuit SW1 is turned ON, electric current flows between thebase and the emitter of the transistor Q3 thereby to turn ON thetransistor Q3. When the transistor. Q3 is turned ON, electric currentflowing between the base and the emitter of the transistor Q4 isinterrupted thereby to turn OFF the transistor Q4. As a result, thepotential of the analog signal terminal 44 is pulled up to the potentialof the DC power source Vcc via the resistor R4.

Also, when the transistor Q1 of the switch circuit SW1 is turned ON, thepotential of the digital signal terminal 45 is pulled up to thepotential of the DC power source Vcc via the resistors R6 and R8. Thepotential of the digital signal terminal 46 is also pulled up to thepotential of the DC power source Vcc via the resistors R7 and R9.

On the other hand, when the transistor Q1 of the switch circuit SW1 isturned OFF, electric current flowing between the base and the emitter ofthe transistor Q3 is interrupted thereby to turn OFF the transistor Q3.When the transistor Q3 is turned OFF, electric current flows between thebase and the emitter of the transistor Q4 thereby to turn ON thetransistor Q4. As a result, the potential of the analog signal terminal44 is set to the GND.

Also, when the transistor Q1 of the switch circuit SW1 is turned OFF,the potential of the digital signal terminal 45 is set to the GND viathe resistors R6, R8, R14 and R15. The potential of the digital signalterminal 46 is also set to the GND via the resistors R7, R9, R14 andR15.

The battery 40 of the present embodiment is provided with a GND terminal47 for setting a reference potential of the battery circuit 42. The GNDterminal 47 is connected to the GND line of the charging circuit 20. Inother words, the reference potential of the battery circuit 42 is set tothe GND of the charging circuit 20. The reference potential of thecontrol unit 24 is also set to the GND of the charging circuit 20.

Hereinafter, a battery circuit protection process executed by thecontrol unit 24 (more particularly, by the CPU 241) will be explained.The control unit 24 is activated, and executes the present process, whenthe plug 11 is connected to the socket 30 and electric power is suppliedto the charging apparatus 1.

As shown in FIG. 5, in the present process, after the logic level of thedesignated temperature detection signal is firstly set to “High” (S100),attachment of the battery 40 to the main body 13 is awaited (S110: No).In S110, whether or not the battery 40 is attached to the main body 13is determined by determining whether or not a signal indicating that thebattery 40 has been attached to the main body 13 is supplied from thebattery circuit 42. In the present embodiment, the signal indicating theattachment of the battery 40 is supplied from the battery circuit 42 tothe control unit 24 via the analog signal terminal 44 and the digitalsignal terminal 45.

When it is determined that the battery 40 has been attached to the mainbody 13 (S110: Yes), a command to start charging is sent to the controlIC 22 so that charging current is outputted from the converter 21 to thebattery 40, thereby to start charging the battery 40 (S120).

It is then determined, based on a signal supplied from the batterycircuit 42, whether or not the battery 40 is fully charged (S130). Whenit is determined that the battery 40 is not fully charged (S130: No),the voltage value of the temperature detection signal (detectiontemperature) supplied from the temperature detection circuit 23 isobtained (S 140). It is then determined whether or not the obtaineddetection temperature is a preassigned designated temperature T orhigher (S150). In the present embodiment, a maximum temperature which isallowable for the battery circuit 42 to operate (for example, 80° C.) ora temperature lower than the maximum temperature is set as thedesignated temperature T.

When it is determined that the detection temperature is lower than thedesignated temperature T (S150: No), the present process returns toS130.

On the other hand, if it is determined that the detection temperature isthe designated temperature T or higher (S150: Yes), a command to stopcharging is sent to the control IC 22 so that the charging current fromthe converter 21 to the battery 40 is stopped, thereby to stop chargingthe battery 40 (S160). Subsequently, the logic level of the designatedtemperature detection signal is set to “Low” (S170) to turn OFF thetransistor Q1 of the switch circuit SW1. As a result, power supply tothe battery circuit 42 is interrupted and the operation of the batterycircuit 42 is inhibited.

Subsequently, in the same manner as in 5140, the detection temperatureis obtained (S180). It is then determined whether or not the obtaineddetection temperature is a preset threshold temperature S or lower(S190). The threshold temperature S of the present embodiment is set tobe a temperature lower than the designated temperature T by apredetermined hysteresis preset temperature α (for example, 5° C.).

When it is determined that the detection temperature is higher than thethreshold temperature S (S190: No), the process returns to S180. When itis determined that the detection temperature is the thresholdtemperature S or lower (S190: Yes), the process returns to S120.

In S130, if it is determined the battery 40 is fully charged (S130:Yes), the present process is ended.

That is, as shown in FIG. 6, in the charging circuit 20, when theambient temperature is lower than the designated temperature T, thelogic level of the designated temperature detection signal is set to“High”. As a result, the DC power source Vcc and the power supplyterminal 43 are electrically connected via the switch circuit SW1.Thereby, electric power is supplied to the battery circuit 42 and thebattery circuit 42 is operated.

On the other hand, as shown in FIG. 7, when the ambient temperature hasreached the designated temperature T, the logic level of the designatedtemperature detection signal is set to “Low”. As a result, the switchcircuit SW1 electrically disconnects the DC power source Vcc and thepower supply terminal 43. Thereby, power supply to the battery circuit42 is interrupted and the operation of the battery circuit 42 isinhibited. Also, by the switch circuit SW2, the potentials of the analogsignal terminal 44 and the digital signal terminals 45 and 46 are set tothe GND.

As noted above, in the charging apparatus 1 of the present embodiment,when the ambient temperature has reached the maximum temperature whichis allowable for the battery circuit 42 to operate, the operation of thebattery circuit 42 is inhibited. Thus, it is possible to suppresscausing trouble to the battery circuit 42 by operating the batterycircuit 42 although the ambient temperature has reached the designatedtemperature.

Also, the charging apparatus 1 of the present embodiment is configuredto be electrically connected to the cigarette lighter socket. Thus,electric power can be easily obtained from the cigarette lighter socketnormally provided inside the vehicle.

In the charging apparatus 1 of the present embodiment, by interruptingpower supply to the battery circuit 42, the operation of the batterycircuit 42 can be reliably inhibited.

Also in the charging apparatus 1 of the present embodiment, when theoperation of the battery circuit 42 is inhibited, the potentials of theanalog signal terminal 44 and the digital signal terminals 45 and 46provided in the battery 40 are set to the GND. Therefore, even if avoltage generated by any cause is applied to either of the terminals,the current generated by the voltage does not flow into the batterycircuit 42. The battery circuit 42 can be reliably protected.

In the charging apparatus 1 of the present embodiment, power supply tothe battery circuit 42 is interrupted and the potentials of theaforementioned terminals are set to the GND, in synchronization withsetting of the logic level of the designated temperature detectionsignal to “Low”. Therefore, as compared to a case in which interruptionof power supply to the battery circuit 42 and setting of the potentialsof the aforementioned terminals to the GND are performed asynchronously,the battery circuit 42 can be efficiently protected.

Although one embodiment of the present invention has been describedabove, it is to be understood that the present invention should not belimited to the above embodiment, but may be embodied in various formswithin the technical scope of the present invention.

For example, in the above embodiment, electric power is supplied fromthe DC power source Vcc to the battery circuit 42. However, electricpower may be supplied to the battery circuit 42 via the converter 21. Inthis case, the operation of the battery circuit 42 may be inhibited byelectrically disconnecting the converter 21 and the battery circuit 42,

In the above described embodiment, the battery 40 is a battery for usein electric power tools. However, the battery 40 can be a battery usedfor apparatus other than electric power tools.

Also, while the program of the battery circuit protection process isprestored in the ROM 242 of the control unit 24 in the above describedembodiment, the program of the battery circuit protection process may bestored in other storage (for example, in a backup RAM) to be loaded fromthe other storage to the control unit 24 (particularly, the CPU 241), ormay be loaded via a network to the control unit 24, for use.

Also, the aforementioned program may be recorded in recording mediawhich can be read by the control unit 24. Such recording media include,for example, a flexible disk (FD), an optical disk (MO), a DVD, aCD-ROM, a Blu-Ray disk, a HD-DVD, a hard disk, a USB memory, a memorycard, etc.

While the charging apparatus 1 is configured to charge the battery 40detached from the electric power tool in the above described embodiment,the charging apparatus 1 may be configured to charge a battery fixed tothe electric power tool. In this case, the electric power tool itselfmay be electrically connected to the charging apparatus 1.

In the above described embodiment, when the operation of the batterycircuit 42 is inhibited, the potentials of the analog signal terminal 44and the digital signal terminals 45 and 46 are set to the GND. However,the potentials may be set to a potential other than the GND as long asthe battery circuit 42 can be electrically protected by that potential.For example, in case that the battery circuit 42 needs to be protectedfrom reverse voltage, the potentials of the aforementioned terminals maybe set to the potential of the DC power source Vcc.

While the temperature detection circuit 23 is provided inside the mainbody 13 in the above described embodiment, the temperature detectioncircuit 23 may be provided outside the main body 13.

In the above described battery circuit protection process, the logiclevel of the designated temperature detection signal is set to “High” inthe first step (S100). However, the step of obtaining the detectiontemperature may be executed before the first step. When the obtaineddetection temperature is the designated temperature T or higher, thelogic level of the designated temperature detection signal may be set to“Low” (that is, the logic level of the designated temperature detectionsignal does not need to be set to “High”).

While the battery 40 is provided with one power supply terminal 43 inthe above described embodiment, the battery 40 may be provided with aplurality of power supply terminals 43.

In the above described embodiment, when the ambient temperature is lowerthan the designated temperature T, the logic level of the designatedtemperature detection signal is set to “High”, while, when the ambienttemperature has reached the designated temperature T, the logic level ofthe designated temperature detection signal is set to “Low”. However,when the ambient temperature is lower than the designated temperature T,the logic level of the designated temperature detection signal may beset to “Low”, while, when the ambient temperature has reached thedesignated temperature T, the logic level of the designated temperaturedetection signal may be set to “High”. In this case, however, the switchcircuit SW1 may be configured such that, when the logic level of thedesignated temperature detection signal is “Low”, the DC power sourceVcc and the power supply terminal 43 are electrically connected, while,when the logic level of the designated temperature detection signal is“High”, the DC power source Vcc and the power supply terminal 43 areelectrically disconnected.

In the present embodiment, the control unit 24 is a microcomputer.However, the control unit 24 may be an electronic circuit other than amicrocomputer, for example, an ASIC (Application Specific IntegratedCircuit), a programmable logic device (for example, FPGA) and others.

1. A charging apparatus, comprising: a connecting unit that is electrically connected to a power supply portion; a charging unit that supplies at least a part of electric power supplied from the power supply portion via the connecting unit to a battery thereby to charge the battery; a temperature detecting unit that detects an ambient temperature; and an operation inhibiting unit that inhibits operation of a battery circuit as an electronic circuit provided in the battery when the temperature detected by the temperature detecting unit has reached a preassigned designated temperature.
 2. The charging apparatus according to claim 1, wherein the designated temperature is set as a maximum temperature which is allowable for the battery circuit to operate.
 3. The charging apparatus according to claim 1, wherein the designated temperature is set as a temperature lower than a maximum temperature which is allowable for the battery circuit to operate.
 4. The charging apparatus according to claim 1, wherein the connecting unit is configured to be electrically connected to a cigarette lighter socket which is provided inside a vehicle in order to supply electric power to a cigarette lighter for lighting a cigarette.
 5. The charging apparatus according to claim 1, further comprising a power supply unit that supplies electric power to the battery circuit, wherein the operation inhibiting unit inhibits the operation of the battery circuit by interrupting power supply from the power supply unit to the battery circuit.
 6. The charging apparatus according to claim 5, wherein the battery is provided with at least one power supply terminal for electrically connecting the battery to the power supply unit and supplying electric power supplied from the power supply unit to the battery circuit, and the operation inhibiting unit inhibits the operation of the battery circuit by interrupting electrical connection between the power supply unit and the at least one power supply terminal.
 7. The charging apparatus according to claim 6, further comprising an electric signal communicating unit that communicates electric signals with the battery circuit, wherein the battery is provided with at least one connecting terminal for electrically connecting the electric signal communicating unit and the battery circuit, and the operation inhibiting unit sets a potential of the at least one connecting terminal to a protective potential by which the battery circuit can be electrically protected, when inhibiting the operation of the battery circuit.
 8. The charging apparatus according to claim 7, wherein the operation inhibiting unit includes an inhibition signal outputting unit that outputs an inhibition signal that inhibits the operation of the battery circuit when inhibiting the operation of the battery circuit; an interrupting unit that, when the inhibition signal is outputted from the inhibition signal outputting unit, interrupts electrical connection between the power supply unit and the at least one power supply terminal; and a protective potential setting unit that, when the electrical connection between the power supply unit and the at least one power supply terminal is interrupted by the interrupting unit, sets a potential of the at least one connecting terminal to the protective potential.
 9. The charging apparatus according to claim 7, wherein the protective potential is a reference potential of the battery circuit.
 10. The charging apparatus according to claim 8, wherein the protective potential is a reference potential of the battery circuit.
 11. The charging apparatus according to claim 1, further comprising a battery attaching portion that detachably attaches the battery to the charging apparatus.
 12. The charging apparatus according to claim 1, wherein the battery is used in an electric power tool.
 13. The charging apparatus according to claim 1, further comprising: a charging stopping unit that stops charging the battery by the charging unit when the temperature detected by the temperature detecting unit has reached the designated temperature; and a charging restarting unit that restarts charging the battery by the charging unit when the temperature detected by the temperature detecting unit has reached a threshold temperature lower than the designated temperature by a predetermined preset hysteresis temperature after the charging stopping unit stops charging the battery.
 14. The charging apparatus according to claim 1, wherein the charging unit supplies the at least a part of electric power to the battery via a first connecting terminal; the charging apparatus further comprising a power supply unit that supplies electric power to the battery circuit via a second connecting terminal that is distinct from the first connecting terminal. 